JP5321332B2 - Dynamic pressure gas bearing - Google Patents

Description

  The present invention relates to bearings used in high-speed rotating machines such as aircraft air cycle machines, helium liquefaction equipment expansion turbines, automobile turbochargers, and the like, and in particular, a fixed member to which a shaft is attached and a rotational pressure provided on the shaft. The present invention relates to a dynamic pressure gas bearing that supports a load by a gas film formed between the first and second portions.

  As a bearing used for a high-speed rotating machine, a thin gas film is formed between the two members by a wedge-shaped space formed between a fixed member to which the shaft is attached and a rotary pressure receiving portion provided on the shaft. 2. Description of the Related Art A dynamic pressure gas bearing that supports a load by a lubricating action of a film is conventionally known.

  As an example of such a conventional dynamic pressure gas bearing, a flexible foil portion that is locked to a fixed member is provided, and the rotation pressure receiving portion from the initial wedge-shaped space between the foil portion and the rotation pressure receiving portion is provided. A configuration is considered in which a plurality of gas films are repeatedly formed between adjacent support protrusions by bending the foil by the pressure of the gas introduced into the gap between the foils. As the foil portion used in such a configuration, a bump foil locked to a fixing member and an upper foil disposed between the bump foil and the rotation pressure receiving portion are provided, and the upper foil and the rotation are provided. A mode of forming a gas film in a space between the pressure receiving unit and the pressure receiving unit is widely known. (See Patent Document 1).

  By the way, in the configuration of this type of conventional dynamic pressure gas bearing, the atmospheric pressure is small at both ends in the circumferential direction, both ends in the axial direction in journal bearings, and both ends in the radial direction in thrust bearings. And the deflection of the upper foil is small. On the other hand, since it is necessary to avoid contact between the rotating pressure receiving portion and the upper foil, it is necessary to secure a gap between the rotating pressure receiving portion and the upper foil even in a portion where the deflection amount of the bump foil and upper foil is small. is there. Then, the width of the gap increases at a portion where the amount of deflection is large, and the pressure of the gas film decreases.

  Patent Document 1 describes a mode in which elastic bodies having different spring constants when elastically biasing the upper foil toward the shaft are arranged between the upper foil and the fixing member in order to prevent the occurrence of such a problem. Has been. When the bump foil described above is employed as the elastic body, in the journal bearing, the distance between the adjacent convex portions of the bump foil at both ends in the axial direction is increased to ensure the amount of deflection at both ends in the axial direction, and the entire upper A configuration in which the foil and the bump foil are bent uniformly is conceivable. However, in such a configuration, the upper foil at the portion corresponding to the portion between the convex portions is greatly deflected, and the pressure of the gas film is reduced at such a portion. Further, when the distance between the convex portions is changed corresponding to the pressure distribution of the gas film, there is a problem that the number of parts and the number of processing steps increase correspondingly.

JP 2003-262222 A

  In order to solve the above-described problems, the present invention provides a gas film by uniformly deflecting the upper foil and the bump foil over the whole while keeping the distance between the convex portions adjacent in the circumferential direction at a predetermined pitch. It is configured to ensure the atmospheric pressure.

An upper foil that is provided between the shaft and a fixing member to which the shaft is attached, and forms a gas film between the shaft and the shaft when the shaft rotates, and between the upper foil and the fixing member A bump foil that is provided with a plurality of protrusions for elastically biasing the upper foil toward the shaft side and spaced apart at a predetermined pitch in the circumferential direction. A notch portion provided with a reduced width is provided to reduce the spring constant of the bump foil when the foil is elastically biased toward the shaft side, and the notch portion is provided with the convex portion. It is provided only in the site | part spaced apart from the vertex of the circumferential direction .

If this is the case, the spring constant of the bump foil can be reduced in correspondence with the atmospheric pressure of the gas film by enlarging the notch at the portion where the atmospheric pressure of the gas film is reduced. While maintaining the distance between the convex portions adjacent to each other at a predetermined pitch, it is possible to realize a configuration in which the bump foil and the upper foil are uniformly bent and the pressure of the gas film is ensured.
Furthermore, since the notch is provided only in a portion spaced circumferentially from the apex of the convex portion, the notch is formed at the apex of the convex portion, which is a portion where the bump foil directly supports the upper foil. By not providing the upper foil, the upper foil can be supported in a wider area. Therefore, the upper foil can be more stably supported by the bump foil.

  In particular, the bump foil is provided with a plurality of slits extending in the circumferential direction, the protrusions are provided between the slits, and the protrusions are provided at the same pitch and opposite phase in the adjacent region across the slit. If it is a thing, since the site | part between convex parts does not continue in an axial direction, gas leak can be decreased.

  On the other hand, the bump foil is provided with a plurality of slits extending in the circumferential direction, the projections are provided between the slits, and the projections are provided at the same pitch and the same phase in an adjacent region across the slit. If it is a thing, formation of the said convex part which adjoins using the same metal mold | die can be performed simultaneously, Therefore Formation of the said convex part can be performed easily.

  In such a dynamic pressure gas bearing, in order to bend the upper foil more uniformly, it is desirable that the size of the notch is increased toward the end in the axial direction. This is because, as described above in the description of the background art, the atmospheric pressure is reduced at both ends in the axial direction.

  Here, in order to ensure that the upper foil and the bump foil can be positioned with respect to the fixing member, each of the upper foil and the bump foil has fins for supporting the fixing member at one end thereof. It is desirable that a locking hole for accommodating the fin is provided on the fixing member side.

  Moreover, in order to make the surface shape of the gas film more smoothly continuous, a mode in which an underfoil is further provided between the upper foil and the bump foil in the circumferential intermediate portion can be cited as a preferable aspect. .

  In particular, the fin of the upper foil and the fin of the bump foil are provided on the same side in the circumferential direction, and the fin of the under foil is provided on the opposite side to the fins of the upper foil and the bump foil. For example, under pressure from the gas film, the upper foil and the under foil slide with each other in an attempt to extend to the opposite sides, and the under foil and the bump foil slide with each other in an attempt to extend to the opposite sides. It is possible to obtain a damping effect in which vibration energy is converted into thermal energy associated with sliding friction.

  In addition, in such a dynamic pressure gas bearing, there is one in which the slit is provided over the entire circumferential direction. Even in this case, the size of the notch can be changed according to the position in the axial direction while making the design common by making the pitch of the convex part of each upper foil divided by the slit the same. Thus, the spring constant can be adjusted more finely.

  In particular, if each of the bump foils divided by the slit is provided with a fin for supporting the fixing member at one end in the circumferential direction, each divided bump foil is stably positioned with respect to the fixing member. can do.

  Further, as another example of the attachment manner of the upper foil, the upper foil has fins for supporting the fixing member at the other end portion, and is associated with fins positioned at both ends of the upper foil. The thing which provided the stop hole in the fixing member side is mentioned.

  According to the structure of the dynamic pressure gas bearing according to the present invention, the upper foil that forms a gas film with the shaft during rotation of the shaft, and the upper foil and the fixing member are disposed between the upper foil and the fixing member. A bump foil that is provided with a plurality of protrusions for elastically biasing the upper foil toward the shaft side and spaced apart in the circumferential direction. The bump foil has a protrusion on the shaft side. In order to reduce the spring constant of the bump foil when elastically energizing, a notch portion provided with a reduced width dimension is further provided, so the notch portion is enlarged at a portion where the pressure of the gas film is reduced. Thereby, the spring constant of the said convex part can be made small corresponding to the atmospheric pressure of a gas film. Therefore, it is possible to realize a configuration in which the bump foil and the upper foil are uniformly bent and the pressure of the gas film is ensured while keeping the distance between the convex portions adjacent in the circumferential direction at a predetermined pitch.

Schematic which shows the dynamic pressure gas bearing which concerns on 1st embodiment of this invention. The general | schematic expanded view which shows the bump foil which concerns on the same embodiment. The perspective view which expands and shows the principal part of the bump foil which concerns on the same embodiment. The general | schematic expanded view which shows the bump foil which concerns on the other embodiment of this invention. The general | schematic expanded view which shows the bump foil which concerns on the other embodiment of this invention. The perspective view which expands and shows the principal part of the bump foil which concerns on the embodiment. The general | schematic expanded view which shows the underfoil which concerns on the other embodiment of this invention. The perspective view which expands and shows the principal part of the bump foil which concerns on the embodiment. The general | schematic expanded view which shows the underfoil which concerns on the other embodiment of this invention. The perspective view which expands and shows the principal part of the bump foil which concerns on the embodiment. The general | schematic expanded view which shows the underfoil which concerns on the other embodiment of this invention. Schematic which shows the dynamic pressure gas bearing which concerns on the other embodiment of this invention. The perspective view which expands and shows the principal part of the bump foil which concerns on the embodiment. Schematic which shows the dynamic pressure gas bearing which concerns on the other embodiment of this invention.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  The bearing according to the present embodiment is a journal bearing as schematically shown in FIG. 1, and includes a foil portion 4 provided between the fixing member 1 and the shaft 2 to which the shaft 2 is attached, and A gas film S is formed between the foil portion 4 and the shaft 2.

  As shown in FIG. 1, the foil portion 4 has a plurality of convex portions 52 that can be almost entirely attached to the fixing member 1 and can be elastically projected and retracted with respect to the fixing member 1. A bump foil 5 disposed on the member 1 side, and an upper foil 6 that forms a gas film S including the wedge-shaped space between the bump foil 5 and the rotary pressure receiving portion 3 are provided. To do. Here, a development view of the bump foil 5 is shown in FIG. In FIG. 1, the bump foil 5 and the upper foil 6 are shown to have a constant thickness for easy understanding of the shape, but the actual thickness dimension is, for example, 0.1 to 0.2 mm. And is formed in an annular shape around which the shaft 2 is wound.

  In the present embodiment, six upper foils 6 and six bump foils 5 are provided. Further, one bump foil 5 is arranged on the fixing member 1 side of each upper foil 6. The number of the upper foil 6 and the bump foil 5 may be arbitrarily set, and the number of the upper foil 6 and the bump foil 5 does not have to be the same.

  Further, as shown in FIG. 1, the upper foil 6 and the bump foil 5 both have fins 61 and 51 at one end edge, and the fixing member 1 side is engaged with the fins 61 and 51. A locking hole 1x that can lock the upper foil 6 and the bump foil 5 is provided. The locking hole 1x engages with the fin 61 of any one of the upper foils 6 and the fins 51 of the bump foil 5 positioned between the upper foil 6 and the fixing member 1 at the same time.

  As shown in FIG. 2, the bump foil 5 is provided with a first slit 5s at a position displaced from the both ends of the bump foil 5 in the axial direction by a predetermined distance d1. Further, a second slit 5t is provided at a position further displaced from the first slit 5s to the center in the axial direction by a predetermined distance d1. And while providing the 1st convex part 52a in the area | region outside the said 1st slit 5s, the 2nd convex part 52b is provided in the area | region between the said 1st slit 5s and the 2nd slit 5t. Provided. Here, an enlarged perspective view of the first convex portion 52a is shown in FIG. Furthermore, the distance between the second slits 5t and 5t is also set to the predetermined distance d1, and a third convex portion 52c is provided in the region between the second slits 5t and 5t. Here, the first, second, and third convex portions 52a, 52b, and 52c are provided at a predetermined pitch in this embodiment. That is, the distance between the first protrusions 52a adjacent to each other in the circumferential direction, the distance between the second protrusions 52b, and the distance between the third protrusions 52c are all the same. In the present embodiment, the circumferential position of the first convex portion 52a, the circumferential position of the second convex portion 52b, and the circumferential position of the third convex portion 52c are set to be the same. ing. An attachment portion that is in surface contact with the fixing member 1 is provided at a portion between the first protrusions 52a, a portion between the second protrusions 52b, and a portion between the third protrusions 52c. 53 is provided. The bump foil 5 has a symmetrical shape in the axial direction. Furthermore, the surfaces of the first, second, and third protrusions 52a, 52b, and 52c are formed in a cylindrical shape in this embodiment.

  Therefore, in the present embodiment, the first and second convex portions 52a and 52b are provided so as to reduce the spring constant at both ends in the axial direction of the bump foil 5 when the upper foil 6 is elastically biased toward the axial side 2. In addition, first and second cutout portions 52ax and 52bx provided by reducing the width direction are provided. Hereinafter, when the first and second convex portions 52a and 52b are collectively referred to without distinction, they are simply referred to as “convex portions 52”. When the first and second cutout portions 52ax and 52bx are collectively referred to without distinction, they are referred to as “cutout portions 52x”. Further, in the present embodiment, the first and second cutout portions 52ax and 52bx are not formed in a portion where the bump foil 5 directly supports the upper foil 6, that is, a portion near the apex of the convex portion 52. It is formed only in a portion spaced in the circumferential direction from the apex of the convex portion 52, that is, a portion adjacent to the contact portion 53. And the notch part 52x located in the axial direction edge part side is set large. Specifically, the cutout width of the first cutout portion 52ax located on the axial direction end side with respect to the second cutout portion 52bx is increased.

  Here, when the shaft 2 rotates, the air in the gap between the shaft 2 and the foil portion 4 is pulled by the viscosity of the air, and the pressure of the gas film S increases. Due to this pressure increase, first, the upper foil 6 is subjected to an action toward the fixing member 1 side. At this time, the upper foil 6 is pressed against the convex portion 52 of the bump foil 5, and the bump foil 5 is subjected to an action toward the fixing member 1 side. In response to this action, the convex portion 52 is elastically deformed to change the surface shape of the bump foil 5. On the other hand, the upper foil 6 receives an upward elastic force from the convex portion 52. For example, the elastic force is small at both axial end portions of the gas film S, and has a predetermined magnitude larger than the elastic force at both axial end portions of the gas film S at the axial intermediate portion. Since the upper foil 6 receives such an elastic force from the convex portion 52, the pressure of the gas film S becomes smaller toward the both ends in the axial direction, so that the shape of the gas film S is substantially over the entire area in the axial direction. A constant width is maintained, and an increase in air pressure occurs in the upper part of the convex portion 52. This pressure rise causes the bearing to support the shaft 2 in a non-contact manner.

  As described above, in the structure of the dynamic pressure gas bearing according to the present embodiment, the notch portions 52x are provided at both ends in the axial direction in which the pressure of the gas film S is reduced, thereby corresponding to the pressure of the gas film S. Thus, the spring constant of the convex portion 52 of the bump foil 5 is reduced. Accordingly, it is possible to realize a configuration in which the bump foil 5 and the upper foil 6 are uniformly deflected and the pressure of the gas film S is ensured while maintaining the configuration in which the convex portions 52 are installed at the same interval throughout the entire area.

  Further, since the circumferential position of the first convex portion 52a and the circumferential position of the second convex portion 52b are set to be the same, the first and second portions are utilized using the same mold. The convex portions 52a and 52b can be formed simultaneously. Therefore, it is possible to reduce the number of work steps for forming the first and second convex portions 52a and 52b on the bump foil 5.

  Furthermore, since the first cutout portion 52ax located on the axial end side is larger than the second cutout portion 52bx, the pressure of the gas film S is reduced in such a dynamic pressure gas bearing. The deformation amount of the bump foil 5 can be ensured at both axial ends. Therefore, the upper foil 6 can be bent more uniformly.

  In addition, the notch portion 52x is provided only in a portion spaced circumferentially from the apex of the convex portion 52, that is, a portion adjacent to the attachment portion 53, and the bump foil 5 directly supports the upper foil 6. Since the notch 52x is not provided in the vicinity of the apex of the convex portion 52 which is a portion to be formed, the upper foil 6 can be brought into contact with the bump foil 5 in a wider area. Therefore, the upper foil 6 can be more stably supported by the bump foil 5.

  Further, instead of the first embodiment described above, a second embodiment described below may be adopted. Here, the dynamic pressure gas bearing in the first embodiment and the dynamic pressure gas bearing in the second embodiment are different only in the configuration of the bump foil 5 and have the same configuration as that in the first embodiment in other points. . Hereinafter, the configuration of the bump foil 5 in the present embodiment will be described. In addition, the same name and code | symbol are attached | subjected to the site | part corresponding to the thing in 1st embodiment.

  The bump foil 5 has a fin 51 at one end edge, as shown in a developed view of FIG. 4 and as in the first embodiment. The fin 51 is for positioning the bump foil 5 with respect to the fixing member 1 by engaging with a locking hole 1x provided on the fixing member 1 side.

  As in the first embodiment, the bump foil 5 is provided with a first slit 5s at a position displaced from the both ends in the axial direction of the bump foil 5 to the center in the axial direction by a predetermined distance d1. A second slit 5t is provided at a position further displaced from the first slit 5s to the axial center by a predetermined distance d1. And in the area | region outside the said 1st slit 5s, between the 2nd convex part 52b and the 2nd slits 5t and 5t between the 1st convex part 52a and the 1st slit 5s and the 2nd slit 5t The 3rd convex part 52c is provided in each site | part. Further, the first and second protrusions 52a and 52b are respectively provided with first and second notches 52ax and 52bx provided by reducing the width direction. In addition, the attachment between the first protrusion 52 a, the second protrusion 52 b, and the third protrusion 52 c is a surface contact with the fixing member 1. A portion 53 is provided. And the notch part 52x located in the axial direction edge part side is set large. Specifically, the cutout width of the first cutout portion 52ax located on the axial direction end side with respect to the second cutout portion 52bx is increased.

  Therefore, in this embodiment, unlike the first embodiment, the first, second, and third protrusions 52a, 52b, 52c are provided at the same pitch and in opposite phases. That is, the circumferential position of the second convex portion 52b is set to a position corresponding to the middle in the circumferential direction of the two first convex portions 52a, and the circumferential position of the third convex portion 52c is set to 2 It is set at a position corresponding to the middle in the circumferential direction of the two second convex portions 52b.

  Even if such an aspect is adopted, the notch portions 52x are provided at both axial ends where the pressure of the gas film S is reduced, and the spring constant of the bump foil 5 is reduced corresponding to the pressure of the gas film S. That is, the configuration in which the bump foil 5 and the upper foil 6 are uniformly bent and the pressure of the gas film S is secured can be realized while maintaining the configuration in which the convex portions 52 are installed at the same interval over the entire area. The effect which can be obtained can be acquired.

  In addition, the second protrusion 52b is positioned between the contact portion 53 between the first protrusions 52a and 52a and the contact portion 53 between the third protrusions 52c and 52c, and the shaft A third protrusion is provided between the contact portion 53 between the second protrusions 52b and 52b near the one end in the direction and the contact portion 53 between the second protrusions 52b and 52b near the other end in the axial direction. The part 52c is located. That is, the space formed on the axial side of the contact portion 53 is not continuous in the axial direction, and gas leakage from the gas film S can be reduced. Therefore, the pressure of the gas film S can be held more effectively.

  The present invention is not limited to the embodiment described above.

  For example, in the first and second embodiments described above, the notches 52x are provided on both sides in the width direction of the convex portion 52. FIG. 5 is an exploded view of the bump foil 5, and an enlarged perspective view of the first convex portion 52a. As shown in FIG. 6, first and second notches 52 ax and 52 bx may be provided at the center in the width direction of the first and second protrusions 52 a and 52 b, respectively. 7 is a development view of the bump foil 5, and an enlarged perspective view of the first convex portion 52a is shown in FIG. 8, respectively. The first and second convex portions 52a and 52b are arranged only on one side in the width direction. And the 2nd notch part 52ax and 52bx may be provided, respectively. 9 is a developed view of the bump foil 5, and an enlarged view of the first convex portion 52a is shown in FIG. 10, respectively, the entire circumferential direction including the vicinity of the apexes of the first and second convex portions 52a and 52b. The first and second cutout portions 52ax and 52bx may be provided by reducing the width direction.

  In the above description, the bump foil 5 is divided into five regions having the same width by the first and second slits 5s and 5t. However, the widths of the regions divided by the slits need to be all equal. Absent. For example, as shown in a developed view in FIG. 11, only the first slit 5s is provided in the bump foil 5, and the region between the first convex portion 52a and the first slit 5s is provided in the region outside the first slit 5s. The third protrusions 52c may be formed respectively, and the notches 52ax may be provided only in the first protrusions 52a. In the first and second embodiments described above, the distance between the axial edge of the bump foil 5 and the first slit 5s is smaller than the distance between the first slit 5s and the second slit 5t. A mode in which the distance between the first slit 5s and the second slit 5t is made smaller than the distance between the second slits 5t and 5t is also conceivable. By adopting this aspect, the difference in spring constant between the first, second, and third convex portions 52a, 52b, 52c can be increased without taking the first and second cutout portions 52ax, 52bx larger. . That is, the main effect of the present invention can be obtained while maintaining the rigidity of the bump foil 5.

  In addition, the bump foil 5 is formed in a wavy shape as shown in FIGS. 12 and 13 in place of the aspect in which the contact portion that is in surface contact with the inner surface of the fixing member is provided between the bump foil convex portions. You may employ | adopt the aspect which provides the 1st and 2nd convex parts 52a and 52b.

  Furthermore, a slit extending over the entire region in the circumferential direction may be provided in the bump foil, and the bump foil may be divided into a plurality of foil pieces. In this case, in order to ensure that the positioning of each foil piece relative to the fixing member can be performed, a fin for supporting the fixing member on the circumferential end of each foil piece may be provided.

  Then, as shown in FIG. 14, an under foil 7 may be provided between the bump foil 5 and the upper foil 6. In this case, the fin 51 of the bump foil 5 and the fin 61 of the upper foil 6 are provided at the upstream edge of the gas flow of the gas film S, and the under foil is provided at the downstream edge of the gas flow of the gas film S. Seven fins 71 may be provided. If comprised in this way, the surface shape of the gas film S can be continued more smoothly. Also, the bump foil 5 and the underfoil 7 try to extend to the opposite sides in response to the pressure from the gas film S, and the underfoil 7 and the upper foil 6 also try to extend to the opposite sides. Therefore, the bump foil 5, the under foil 7, and the upper foil 6 slide on each other. Therefore, it is possible to obtain a damping effect in which the vibration energy of the bump foil 5, the under foil 7 and the upper foil 6 is converted into thermal energy associated with sliding friction, and the generation of vibration and noise is suppressed by this damping effect. can do. Of course, fins 51 of the bump foil 5 and fins 61 of the upper foil 6 are provided at the downstream edge of the gas flow of the gas film S, and fins 71 of the underfoil 7 are provided at the upstream edge of the gas flow. Even if it is an aspect to provide, such an effect can be acquired.

  In addition, fins for supporting the fixing member on the upstream edge and the downstream edge of the upper foil of the dynamic pressure gas bearing according to the embodiment as described above are provided, and both circumferential ends of the upper foil are provided. A locking hole may be provided on the fixing member side in correspondence with the fins respectively positioned on the fixing member. Even in such a case, the upper foil can be reliably positioned with respect to the fixing member.

  In addition, various changes may be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Fixed member 1x ... Locking hole 2 ... Shaft 5 ... Bump foil 6 ... Upper foil 51, 61 ... Fin 52 ... Convex part 52a, 52b ... (1st, 2nd) convex part 5s, 5t ... Slit 52x ... Notch 52ax, 52bx ... (first and second) notch

Claims (10)

An upper foil that is provided between the shaft and a fixing member to which the shaft is attached, and forms a gas film between the shaft and the shaft when the shaft rotates, and between the upper foil and the fixing member A bump foil that is provided with a plurality of protrusions for elastically biasing the upper foil toward the shaft side and spaced apart at a predetermined pitch in the circumferential direction. Further provided with a notch provided with a reduced width dimension to reduce the spring constant of the bump foil when elastically biasing the foil to the shaft side ,
The dynamic pressure gas bearing according to claim 1, wherein the notch portion is provided only in a portion spaced circumferentially from the apex of the convex portion . The bump foil is provided with a plurality of slits extending in the circumferential direction, the protrusions are provided between the slits, and the protrusions are provided in an adjacent region across the slits at the same pitch and in opposite phase. The dynamic pressure gas bearing according to 1. The bump foil is provided with a plurality of slits extending in the circumferential direction, the protrusions are provided between the slits, and the protrusions are provided at the same pitch and the same phase in adjacent regions across the slit. The dynamic pressure gas bearing according to 1. The dynamic pressure gas bearing according to claim 1, 2 or 3 , wherein the size of the notch is increased as it goes toward the end in the axial direction . Claims 1 and 2, wherein each of the upper foil and the bump foil has a fin for supporting the fixing member at one end in the circumferential direction, and a locking hole for storing the fin is provided on the fixing member side . The dynamic pressure gas bearing according to 3 or 4. 6. The hydrodynamic gas bearing according to claim 5 , wherein the fins of the upper foil and the fins of the bump foil are provided on opposite sides in the circumferential direction . The dynamic pressure gas bearing according to claim 5 or 6 , further comprising an underfoil between the upper foil and the bump foil . The dynamic pressure gas bearing according to claim 1, wherein the slit is provided over the entire circumferential direction . The dynamic pressure gas bearing according to claim 8, wherein a fin for supporting the fixed member on a circumferential end of each bump foil divided by the slit is provided . The upper foil has fins for supporting the fixing member at the other end in the circumferential direction, and locking holes are provided on the fixing member side corresponding to the fins located at both ends in the circumferential direction of the upper foil. The dynamic pressure gas bearing according to claim 5, 6, 7 or 9.

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